Several methods for determining linear position for audio-fader control have been used. One method is using linear contact. While inexpensive, controls using linear contact method suffer from very poor wear and high drag force by using plastic or carbon resistive elements. A second method uses an inductive component. By using the physical principles of induction in a wire, eddy currents detect the position of an electrically conducting target that is sliding or rotating above a set of coils, consisting of one transmitter coil and two receiver coils. Controls using inductive components provide good linearity and resolution but also require careful calibration. A third method is using on-axis magnetic field, such as described in U.S. Pat. No. 6,813,361. Controls using on-axis magnetic field suffer not only from limited resolution, travel, and linearity, but also are sensitive to mechanical tolerance, magnet strength, Hall sensor offset, and Hall sensor sensitivity. A fourth method is uses optical components. These controls require relatively complex optics and digital pickups have limited resolution and suffer from poor repeatability because of highly sensitive component and mechanical tolerance.
Therefore, there is a need for improved methods and systems for improving fader position measurement.